Mobile machines such as, for example, off-highway haul trucks, motor graders, snow plows, and other types of heavy equipment are used to perform a variety of tasks. Some of these tasks involve carrying or pushing large, awkward, loose, and/or heavy loads up steep inclines or along rough or poorly marked haul roads. And, because of the size and momentum of the machines and/or because of poor visibility, these tasks can be difficult for a human operator to complete effectively.
To help guide the machines along the haul roads and keep the machines within appropriate lanes on the haul roads, some worksites utilize earthen berms located on one side or on both sides of the haul roads. The berms act as borders of the haul road, providing a visual indication of the edge of the road and functioning to either redirect the machine back onto the road or hinder further movement of the machine off of the road, should the machine deviate from an appropriate lane. Although effective, the use of the earthen berms alone may be insufficient to keep some large or heavily loaded machines on the haul roads and, in some situations, may damage the machines when the machines contact the berms. As such, an alternative or additional method for keeping the machines within the appropriate lanes of a haul road may be desirable.
U.S. Patent Publication No. 2010/0010703 to Coats et al., assigned to Caterpillar Inc., discloses a guidance system for such a machine. The guidance system may include a scanning device configured to generate a signal indicative of an actual lateral distance from the machine to a roadway marker, such as a berm. The system may also include a controller configured to compare the actual lateral distance to a desired distance, to keep the machine away from the marker or berm.
In some cases, however, it may not be necessary or desirable to determine the actual lateral distance between the machine and the roadway marker. For example, it may be necessary to collect and/or process large amounts of data to determine the actual lateral distance. Also, when the roadway marker is a berm, objects other than the berm may occasionally be detected, such that the determined lateral distance may not, in fact, be the real distance between the machine and the berm. Thus, the system may not be able to determine whether the machine is at least a minimum desired distance from the berm.
The disclosed guidance system, described in detail below, is directed to providing further advantages over the prior art.